Aromatic rings and aromatic rods: Nonplanar character of an indeno-dehydro 14 annulene

Kévin Cocq (1, 2) , N. Saffon-Merceron (3) , A. Poater (4) , Valérie Maraval (1) , Rémi Chauvin (1, 2)

1 LCC - Laboratoire de chimie de coordination
2 UT3 - Université Toulouse III - Paul Sabatier
3 ICT - Institut de Chimie de Toulouse
4 IQCC - Institut de Química Computacional i Catàlisi and Departament de Química, Universitat de Girona

Since the concept of aromaticity has been proposed to be generalizable to acetylenic rods (linear ring' of [2]annulene), p-diisopropyl-tetraphenyl-carbo-benzene (C48H34) and an indenone-fused isopropyl-triphenyloctadehydro[14]annulene (C42H26O) can be regarded as based on heptacyclic aromatic cores. The formation and X-ray crystal structures of both products are described. The latter has been obtained as a reductive rearrangement product of a transient isopropyl-pentaoxy[5]pericyclyne devised as a putative precursor of a carbo-fulvene target. A mechanism accounting for this peculiar transformation is proposed. Deviation from global planarity is measured by a 6 degrees angle between the mean plane of the indenone bicycle and that of 13 atoms of the [14]annulenic macrocycle, forming dihedral angles with the local plane of the isopropyl-substituted sp(2) vertex of 16 degrees and 15 degrees, respectively. The magnetic aromaticity of the carbo-benzene and indeno-octadehydro[14]annulene products is evaluated by NICS calculations.

Domaines: Chimie de coordination

Kévin Cocq, N. Saffon-Merceron, A. Poater, Valérie Maraval, Rémi Chauvin. Aromatic rings and aromatic rods: Nonplanar character of an indeno-dehydro 14 annulene. SYNLETT, 2016, 27 (14), pp.2105-2112. ⟨10.1055/s-0035-1562720⟩. ⟨hal-01927916⟩